1. Field of the Invention
The present invention relates to a method for producing an L-amino acid using a microorganism. L-amino acids are useful in various applications, such as for ingredients in seasonings, food additives, feed additives, chemicals, and drugs.
2. Brief Description of the Related Art
L-amino acids are industrially produced by fermentation using microorganisms, such as those belonging to the genus Brevibacterium, Corynebacterium, Escherichia, or the like. In such production methods, bacterial strains isolated from nature, artificial mutants of such strains, and microorganisms modified by recombinant DNA techniques so that the activity of a basic L-amino acid biosynthesis enzyme is increased, and so forth have been used (EP0643135B, EP0733712B, EP1477565A, EP0796912A, EP0837134A, WO01/53459, EP1170376A, WO2005/010175, and WO96/17930).
When amino acids are produced using a microorganism, sugars are generally used in the medium as a carbon source, but glycerol has also been used as the carbon source (EP1715055A, EP1715056A).
Ribonuclease G was found to be involved in the maturation of the 5′ end of 16S rRNA (EMBO J., 18 (1999) 2878-2885, Biochem. Biophys. Res. Commun., 259 (1999) 483-488). Furthermore, it is known that ribonuclease G digests an AU-rich region of a single stranded RNA, but the digestion sequence or other details have not yet been elucidated (J. Biol. Chem., 269 (1994) 10797-10803, J. Biol. Chem., 269 (1994) 10790-10796, J. Biol. Chem., 275 (2000) 8726-8732).
Ribonuclease G is highly homologous to the catalytic domain of ribonuclease E. This catalytic domain is located at the N-terminus of ribonuclease E, and this enzyme has been shown to be a major ribonuclease of E. coli. Ribonuclease E is involved in the decomposition of most of mRNAs, as well as the maturation of tRNAs and rRNAs (Genetics, 90 (1978) 659-671, J. Mol. Biol., 129 (1979) 343-357, Cell, 15 (1978) 1055-1066, RNA, 8 (2002) 97-109, Genes Dev., 16 (2002) 1102-1115, J. Mol. Biol., 352 (2005) 22-27). However, it has been found that ribonuclease G does not participate in the maturation of tRNAs and can only partially complement the lethality of E. coli in the absence of the ribonuclease E (EMBO J., 18 (1999) 2878-2885, Biochem. Biophys. Res. Commun., 259 (1999) 483-488).
Since a deficiency of the rng gene coding for ribonuclease G does not affect growth at all under typical laboratory conditions, the ribonuclease E can complement the function of ribonuclease G (EMBO J., 18 (1999) 2878-2885, Biochem. Biophys. Res. Commun., 259 (1999) 483-488, Mol. Gen. Genet., 253 (1997) 515-519).
Although there are a few reports about the physiological role of ribonuclease G, this enzyme has been reported to participate in the decomposition of eno mRNA or adhE mRNA, and to participate in the specific decomposition of mRNAs of multiple genes, including the genes coding for several glycolytic enzymes, on the basis of results of microarray analysis (Mol. Microbiol., 43 (2002) 1445-1456, Genes Cell., 6 (2001) 403-410, Biosci. Biotechnol. Biochem., 66 (2002) 2216-2220).
Moreover, when a strain deficient in both the rng and cra genes is cultured using glucose as the carbon source, pyruvic acid is produced (Appl. Microbiol. Biotechnol., 76 (2007) 183-192).
Furthermore, if the rng gene is deleted in an Escherichia bacterium, pyruvic acid and L-valine are produced (Japanese Patent Application Laid-open (Kokai, JP-A) No. 2005-333855).